Step 1: Understanding the Question:
Solubility of aromatic compounds in water depends on their ability to form intermolecular hydrogen bonds with water molecules. Step 2: Detailed Explanation:
- Phenol: Relatively soluble due to intermolecular H-bonding with water.
- p-Cresol: Has an additional non-polar methyl group which decreases solubility compared to phenol.
- o-Nitrophenol: Undergoes intramolecular hydrogen bonding between the hydroxy group and the nitro group. This significantly reduces the availability of the \( -OH \) group to form hydrogen bonds with water molecules.
- p-Nitrophenol: Forms intermolecular hydrogen bonds with water molecules and is more soluble than the ortho isomer.
As a result, o-nitrophenol has the lowest solubility among the options. Step 3: Final Answer:
o-Nitrophenol has the lowest solubility in water.